Occlusive vascular disease is generally characterized by a hardened, calcified deposit blocking the flow of blood through a blood vessel. Occlusive vascular disease can cause blockages in both coronary and peripheral blood vessels. Particularly serious examples include situations in which the lesion and deposit completely block the vessel, a condition known as chronic total occlusion (CTO). A typical CTO is a lesion located in a blood vessel of a patient that results from an accumulation of deposits, typically calcified fibrin, therein.
Traditionally, this type of disease has been treated by both bypass surgery and/or drug therapy. Recently, it has been discovered that occlusive vascular disease can also be treated by advancing a guidewire through or across the diseased location to create a passageway for interventional treatment, i.e. angioplasty. Alternatively, guiding catheters intended to achieve similar functionality have also been employed. In these procedures, the guidewire is used to puncture through the hard deposit in order to create a pathway for balloon catheter or stent delivery to the lesion site. Techniques in this regard can include what is known in the art as “dottering” by which the device is subjected to short alternating advancing and retrograde movement so the tip or the like that engages the lesion site imparts short thrusts to in a sense peck away at the diseased location.
Typically, a guidewire and a catheter are separate devices that are used in percutaneous transluminal coronary angioplasty (PTCA) procedures, with the guidewire performing essentially a guiding function for the PTCA catheter that effects the desired medical procedure. Accordingly, significant challenges exist in the design of guidewires and guiding catheters. For example, positioning the guiding device at the appropriate location in the patient's anatomy is a difficult process, requiring the navigation of the tortuous vasculature and a successful crossing of the lesion while maintaining the alignment of the tip of the guiding device to prevent perforation of the vessel wall.
Further, guiding devices intended for use in CTO face additional challenges. Often, the true lumen of the vessel is embedded in the occlusion and is surrounded by false lumens that have been created over time. Attempts to cross the true lumen can result in the tip of the guiding device deflecting into the false lumens of the occlusion, which may result in vessel perforation, dissection, or release of plaque particles into the bloodstream. Moreover, during crossing, the tip of the guiding device has a natural tendency to be directed toward the side of the occlusion rather than the center due to the configuration of the occlusion, which can also result in vessel perforation, dissection and inability to cross the occlusion.
As a result, it is advantageous for guiding devices intended for use in CTO procedures with a number of functional features, some of which are opposed by nature, requiring a fine balance to be struck in order to achieve the desired performance. For example, the guiding device must be flexible enough to navigate through tortuous pathways within the body, consisting of bends, loops and branches. However, they also must be sufficiently stiff to provide the necessary pushability to overcome friction and occlusions as they are advanced into position. Guiding devices must also have sufficient stiffness to serve as a conduit for other devices that are advanced over or through them. In addition, guiding devices must be torqueable to facilitate directional changes as they are guided into position.
Therefore, a need remains for a medical device that can be easily positioned prior to and during lesion crossing and/or treatment and also reduces the risk of perforating the blood vessel. It would be advantageous to provide such a guiding device with the flexibility to be advanced through the vasculature while remaining central to the lumen of the vessel. It would also be advantageous to combine the necessary flexibility with the stiffness necessary to cross occluded lesions. Further, it would be advantageous to minimize the possibilities of the tip of guiding device deflecting off the cap of the lesion into the subintimal space. It would also be advantageous to minimize the risk of perforating the vessel wall due to misalignment of the tip of the guiding device. As will be detailed in the discussion follows, this invention satisfies these and other goals.